Ethyl (−)-2-[4-[2-[[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl ]amino]ethyl]-2,5-dimethylphenoxy]acetate represented by formula (II):
has been disclosed in WO00/02846 by the present applicant and is itself a known compound. This compound has been known to have an excellent β3-adrenoceptor stimulating effect and is useful as a medicament for the treatment of pollakiuria or urinary incontinence.
Compound (II) exhibits excellent therapeutic activities for the treatment of pollakiuria or urinary incontinence, while it could have been produced only in amorphous forms by the preparation method as described in WO00/02846. For producing the amorphous compound (II) in a substantially pure form, troublesome purification steps have been required. Compound (II) is difficult to formulate into solid form preparations due to its viscous physical property. Moreover, compound (II) has unsatisfactory stability, and when stored under ordinary conditions for a long period, it has serious problems to discolor and decrease the content of the active ingredient. Accordingly, there is a need for a novel form of compound (II) which has satisfactory storage stability and is usable as a drug substance.